1. Field of the Invention
The present invention relates to a photosensitive transfer recording material. More specifically, it relates to a photosensitive transfer recording material appropriate for dry transfer onto an uneven support, and to a process for producing a color filter using the photosensitive transfer recording material.
2. Description of the Related Art
Photosensitive transfer recording materials that are used in the production of color filters for liquid crystal cells and that comprise a temporary support having successively disposed thereon a thermoplastic resin layer, an alkali-soluble intermediate layer, and an alkali-soluble, pigment-containing photosensitive resin layer are conventionally known. Such materials are disclosed in, for example, Japanese Patent Application Laid-open Publication (JP-A) Nos. 5-173320 and 11-149008. In these publications, a photosensitive resin layer of a photosensitive transfer recording material is adhered to a substrate by ordinary lamination, and then the temporary support is peeled away to form an image on the substrate without exposing and developing the substrate.
Conventionally, there has been the problem that, when the surface of the substrate is uneven, air bubbles come between the photosensitive resin layer and the substrate when the two are adhered, whereby defects in transfer are caused. However, it has become possible to obtain a good transfer image, even if the substrate is uneven, by disposing a thermoplastic resin layer to prevent the formation of air bubbles.
Nevertheless, air bubbles have again become easily formable due to an increase in the production rates of color filters in recent years and an attendant increase in the speed at which lamination is conducted. Thus, defects in transfer have again become a problem.
In order to prevent air bubbles from forming when lamination is conducted at high speed, it is necessary to soften the thermoplastic resin layer. However, softening the thermoplastic resin layer causes reticulation. Reticulation means that when the intermediate layer expands due to moisture absorption or the like, the soft thermoplastic resin buckles and fine wrinkles appear in the surface of the photosensitive transfer recording material, which results in defective transfer. What is needed in order to conduct lamination at high speed is a technique to prevent air bubbles and reticulation.
It is a first object of the present invention to provide a photosensitive transfer recording material that prevents both the formation of air bubbles and reticulation even when lamination is conducted at high speed. It is a second object of the invention to provide a process for producing a color filter using the photosensitive transfer recording material.
In order to achieve the first object, there is provided a photosensitive transfer recording material that includes a temporary support having sequentially disposed thereon a thermoplastic resin layer, an alkali-soluble intermediate layer, and an alkali-soluble pigment-containing photosensitive resin layer, with the intermediate layer containing a polymer latex.
The glass transition temperature (Tg) of the polymer latex is preferably 60xc2x0 C. or less. Additionally, the amount of the polymer latex is, in terms of the solid content thereof, 5 to 70% by weight with respect to the resin of the intermediate layer.
In order to achieve the second object, there is also provided a process for producing a color filter using plural types of the photosensitive transfer recording material.
Photosensitive Transfer Recording Material
A photosensitive transfer recording material of the present invention comprises a temporary support having sequentially disposed thereon a thermoplastic resin layer, an alkali-soluble intermediate layer, and an alkali-soluble pigment-containing photosensitive resin layer, with the intermediate layer containing a polymer latex. The photosensitive transfer recording material of the invention and a process for producing a color filter using the photosensitive transfer recording material are described below.
Alkali-solubility
By xe2x80x9calkali-solublexe2x80x9d is meant soluble in an aqueous solution of an alkaline substance, such as listed below, or soluble in an aqueous solution of an alkaline substance having mixed therein water and a water-miscible organic solvent.
Examples of the alkaline substance include alkali metal hydroxides (such as sodium hydroxide and potassium hydroxide), alkali metal carbonates (such as sodium carbonate and potassium carbonate), alkali metal bicarbonates (such as sodium bicarbonate and potassium bicarbonate), alkali metal silicates (such as sodium silicate and potassium silicate), alkali metal metasilicates (such as sodium metasilicate and potassium metasilicate), triethanolamine, diethanolamine, monoethanolamine, morpholine, tetraalkylammonium hydroxides (such as tetramethylammonium hydroxide) and sodium tertiary phosphate. It is preferable that the concentration of the alkaline substance is 0.01 to 30% by weight and that the pH is 8 to 14.
Examples of the water-miscible organic solvent include methanol, ethanol, 2-propanol, 1-propanol, butanol, diacetone alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, benzyl alcohol, acetone, methyl ethyl ketone, cyclohexane, xcex5-caprolactone, xcex3-butyrolactone, dimethylformamide, dimethylacetamide, hexamethylphosphoramide, ethyl lactate, methyl lactate, xcex5-caprolactam and N-methylpyrrolidone. The concentration of the water-miscible organic solvent is 0.1 to 30% by weight. Known surfactants can also be added. It is preferable that the concentration of the surfactant is 0.01 to 10% by weight.
Thermoplastic Resin Layer
Examples of the resin comprising the thermoplastic resin layer include an acrylic resin, a polystyrene resin, a polyester resin, a polyurethane resin, a rubber resin, a vinyl acetate resin, a polyolefin resin, and copolymers thereof. Although it is not essential for the resin comprising the thermoplastic resin layer of the invention to be alkali-soluble, the resin is preferably alkali-soluble.
Specific examples of the resin comprising the thermoplastic resin layer include at least one of a saponified product of an ethylene/acrylic ester copolymer, a saponified product of a styrene/(meth)acrylic ester copolymer, a styrene/(meth)acrylic acid/(meth)acrylic ester three-component copolymer, a saponified product of a vinyl toluene/(meth)acrylic ester copolymer, a poly(meth)acrylic ester, a saponified product of a butyl (meth)acrylate/(meth)acrylic ester (such as vinyl acetate) copolymer, and the alkaline aqueous solution-soluble organic polymers described in Purasuchikku seinxc3x4 binran (xe2x80x9cManual of Plastics Propertiesxe2x80x9d) (compiled by the Japan Plastics Industry Federation and Zen-Nihon Purasuchikku Seikei Kxc3x4gyxc3x4 Rengxc3x4kai, Tokyo: Kxc3x4gyxc3x4 Chxc3x4sakai, 1968).
It is preferably that these resins are used in combination.
In particular, resins having a weight average molecular weight of 50,000 to 500,000 and a glass transition temperature (Tg) of 0 to 140xc2x0 C. (hereinafter, also referred to as resin (A)) are preferable. Resins having a weight average molecular weight of 60,000 to 200,000 and a glass transition temperature (Tg) of 30 to 110xc2x0 C. are more preferable. Specific examples of these resins include the alkaline aqueous solution-soluble resins described in Japanese Patent Application Publication (JP-B) Nos. 54-34327, 55-38961, 58-12577 and 54-25957, JP-A No. 61-134756, JP-B No. 59-44615, JP-A Nos. 54-92723,54-99418, 54-137085, 57-20732, 58-93046, 59-97135 and 60-159743, Offenlegungsschrift (OLS) No. 3504254, JP-A Nos. 60-247638, 60-208748, 60-214354, 60-230135, 60-258539, 61-169829, 61-213213, 63-147159, 63-213837, 63-266448, 64-55551, 64-55550, 2-191955, 2-199403, 2-199404and 2-208602, and Japanese Patent Application No. 4-39653. Especially preferable is the methacrylic acid/2-ethylhexyl acrylate/benzyl methacrylate/methyl methacrylate copolymer described in JP-A No. 63-147159.
Moreover, resins having a weight average molecular weight of 3,000 to 30,000 and a glass transition temperature (Tg) of 30 to 170xc2x0 C. (hereinafter, also referred to as resin (B)) are preferable. Further, resins having a weight average molecular weight of 4,000 to 20,000 and a glass transition temperature (Tg) of 60 to 140xc2x0 C. are more preferable. Preferable examples thereof include the resins described in the foregoing documents. Especially preferable is the styrene/(meth)acrylic acid copolymer described in JP-B No. 55-38961 and JP-A No. 5-241340.
When resin (A) comprising the thermoplastic resin layer has a weight average molecular weight of less than 50,000 or a glass transition temperature (Tg) lower than 0xc2x0 C., reticulation occurs and the thermoplastic resin bleeds out during transfer and contaminates a permanent support. When resin (A) has a weight average molecular weight of more than 500,000 or a glass transition temperature (Tg) higher than 140xc2x0 C., air bubbles enter between pixels during transfer and it becomes difficult to remove the alkaline aqueous solution of the thermoplastic resin.
When resin (B) constituting the thermoplastic resin layer has a weight average molecular weight of less than 3,000 or a glass transition temperature (Tg) lower than 30xc2x0 C., reticulation occurs and the thermoplastic resin bleeds out during transfer and contaminates the permanent support. When resin (B) has a weight average molecular weight of more than 30,000 or a glass transition temperature (Tg) higher than 170xc2x0 C., bubbles enter between pixels during transfer and it becomes difficult to remove the alkaline aqueous solution of the thermoplastic resin.
When resins (A) and (B) are mixed and used in combination, the mixing ratio of resin (A) is preferably 95 to 5% by weight. When the ratio of resin (A) exceeds 95%, bubbles are liable to enter between pixels during transfer. When the ratio of resin (A) is less than 5%, the thermoplastic resin bleeds out, or the thermoplastic resin layer becomes brittle and it becomes easy for fine chips to be scattered during cutting.
The glass transition temperature (Tg) of the thermoplastic resin layer can be finely adjusted by adding, to these organic polymers, various polymers, a supercooling substance, an adhesion modifier, a surfactant and a release agent for adjusting adhesion with a temporary support and/or transferability. Preferable examples of the plasticizer include polypropylene glycol, polyethylene glycol, dioctyl phthalate, diheptyl phthalate, dibutyl phthalate, tricresyl phosphate, cresyldiphenyl phosphate biphenyldiphenyl phosphate, polyethylene glycol mono(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol mono(meth)acrylate, polypropylene glycol di(meth)acrylate, an addition reaction product of an epoxy resin and polyethylene glycol mono(meth)acrylate, an addition reaction product of an organic diisocyanate and polyethylene glycol mono(meth)acrylate, an addition reaction product of an organic diisocyanate and polypropylene glycol mono(meth)acrylate and a condensation reaction product of bisphenol A and polyethylene glycol mono(meth)acrylate. The amount of the plasticizer is preferably 0 to 200% by weight, and more preferably 20 to 100% by weight, based on the total amount of resins (A) and (B) comprising the thermoplastic resin layer.
The thickness of the thermoplastic resin layer is preferably 6 xcexcm or more. The reason is because, when the thickness of the thermoplastic resin layer is less than 6 xcexcm, it becomes impossible to completely absorb unevenness of an undercoat having a thickness of 1 xcexcm or more. Further, the upper limit is approximately 100 xcexcm or less, and preferably approximately 50 xcexcm or less, in view of removing the alkaline aqueous solution and productivity.
A coating solution of the thermoplastic resin layer in the invention is not particularly limited as long as it dissolves the resin comprising this layer. Examples thereof include methyl ethyl ketone, n-propanol and i-propanol.
Alkali-soluble Intermediate Layer
The resin constituting the intermediate layer is not particularly limited so long as it has the foregoing alkali solubility. Examples of the resin include a polyvinyl alcohol resin, a polyvinyl pyrrolidone resin, a cellulose resin, an acrylamide resin, a polyethylene oxide resin, gelatin, a vinyl ether resin, a polyamide resin, and copolymers thereof. Further, a resin formed by copolymerizing a resin, such as a polyester that is ordinarily alkali-insoluble, with a monomer having a carboxyl group or a sulfonic group to make the resin alkali-soluble may also be used.
Of these resins, a polyvinyl alcohol resin is preferable, and the degree of saponification thereof is preferably 80% or more, and more preferably 83 to 98%.
It is preferable that the resin comprising the intermediate layer is formed by mixing two or more types of resins. It is particularly preferable that the resin is formed by mixing polyvinyl alcohol and polyvinyl pyrrolidone. The polyvinyl pyrrolidone/polyvinyl alcohol weight ratio is preferably 1/99 to 75/25, and more preferably 10/90 to 50/50. When this ratio is less than 1/99, there are problems in that surface conditions of the intermediate layer are compromised and adhesion between the intermediate layer and the photosensitive resin layer formed thereon is poor. When the ratio exceeds 75/25, the ability of the intermediate layer to block oxygen is reduced, whereby sensitivity is reduced.
Additives such as surfactants may be added to the intermediate layer as required.
The thickness of the intermediate layer is preferably 0.1 to 5 xcexcm, and more preferably 0.5 to 3 xcexcm. When the thickness is less than 0.1 xcexcm, the ability of the intermediate layer to block oxygen is reduced. When it is more than 5 xcexcm, it takes longer for the intermediate layer to be removed during development.
The coating solvent of the intermediate layer is not particularly limited as long as it dissolves the resin. Water is preferable. A solvent created by mixing water and the foregoing water-miscible organic solvent is also preferable. Preferable examples of the solvent include water, water/methanol (weight ratio=90/10), water/methanol (weight ratio=70/30), water/methanol (weight ratio=55/45), water/ethanol (weight ratio=70/30), water/1-propanol (weight ratio=70/30), water/acetone (weight ratio=90/10), and water/methyl ethyl ketone (weight ratio=95/5).
Polymer Latex
Polymer latex is added to the intermediate layer of the invention. The polymer latex referred to herein is a dispersion in which fine particles of the water-insoluble polymer are dispersed in water. Examples of such polymer latex are described in, for example, Shxc3x4ichi Muroi""s Kxc3x4bunshi ratekkusu no kagaku (xe2x80x9cChemistry of Polymer Latexxe2x80x9d) (Tokyo: Kxc3x4bunshi Kankxc3x4kai, 1973). As the polymer latex used in the invention, polymer latexes made of an acrylic polymer, a vinyl acetate polymer, a rubber (for example, styrene-butadiene or chloroprene) polymer, an olefin polymer, a polyester polymer, a polyurethane polymer, a polystyrene polymer, and copolymers thereof are preferable.
The glass transition temperature (Tg) of the polymer latex is preferably 60xc2x0 C. or less, and more preferably 45xc2x0 C. or less. When the Tg exceeds 60xc2x0 C., it becomes difficult to prevent reticulation. Preferable examples of the polymer latex include an ethyl acrylate latex (average particle diameter=0.2 xcexcm), an ethyl acrylate/acrylic acid latex (weight ratio=98/2, average particle diameter=0.2 xcexcm), a methyl methacrylate/ethyl acrylate/acrylic acid latex (weight ratio=5/40/5, average particle diameter=0.15 xcexcm), a methyl methacrylate/ethyl acrylate/acrylic acid latex (weight ratio=65/30/5, average particle diameter=0.19 xcexcm), a methyl methacrylate/ethyl acrylate/acrylic acid latex (weight ratio=75/20/5, average particle diameter=0.15 xcexcm), a methyl methacrylate/ethyl acrylate/acrylic acid latex (weight ratio=30/65/5, average particle diameter=0.15 xcexcm), a methyl methacrylate/2-ethylhexyl acrylate/methacrylic acid latex (weight ratio=50/47/3, average particle diameter=0.15 xcexcm) and a styrene/butadiene/acrylic acid latex (weight ratio=40/58/2, average particle diameter=0.15 xcexcm).
The amount of the polymer latex is preferably 5 to 70% by weight, more preferably 10 to 50% by weight, especially preferably 20 to 40% by weight, in terms of the solid content of the polymer latex, with respect to the resin comprising the intermediate layer. When the amount is less than 5% by weight, it becomes difficult to prevent reticulation. When the amount exceeds 70% by weight, surface conditions of the intermediate layer are compromised.
Photosensitive Resin Layer
Known photopolymerizable compositions can be used as the resin comprising the photosensitive resin layer of the invention. Preferable examples thereof are described in Japanese Patent Application No. 2-82262. The resin referred to herein may also be a resin formed by a monomer or an oligomer that is polymerized after exposure.
The photosensitive resin layer of the invention can contain a pigment other than the resin. Types and sizes of preferable pigments are described in, for example, JP-A No. 11-149008.
The photosensitive resin layer of the invention may include, as required, additives such as surfactants. Further, the coating solution of the thermoplastic resin layer of the invention is not particularly limited as long as it dissolves the resin constituting this layer. Examples thereof include methyl ethyl ketone, n-propanol and i-propanol.
It is preferable that a thin coating sheet for protecting the photosensitive resin layer from contamination or damage during storage is formed on the photosensitive resin layer. The coating sheet may be formed of a material that is the same as or similar to the material of the temporary support, provided that it can easily be separated from the photosensitive resin layer. Examples of the material for the coating sheet include a silicone sheet or a polyolefin or polytetrafluoroethylene sheet. The thickness of the coating sheet is preferably approximately 5 to 100 xcexcm. A polyethylene or polypropylene film having a thickness of 10 to 30 xcexcm is especially preferable.
Temporary Support
Known supports made of polyester, polystyrene or the like can be used as the temporary support of the invention. A biaxially oriented polyethylene terephthalate support is preferable in view of costs, heat resistance and dimensional stability. The thickness of the temporary support is preferably 15 to 200 xcexcm, and more preferably 30 to 150 xcexcm. When the thickness is less than 15 xcexcm, wrinkles are generated by heat during lamination. When the thickness exceeds 200 xcexcm, costs escalate.
Moreover, the electroconductive layer described in JP-A No. 11-149008 may be formed on the temporary support as required.
Image Forming Method
An image forming method using the photosensitive transfer recording material of the invention is described below.
First, the coating sheet of the photosensitive transfer recording material is removed, and the photosensitive resin layer is adhered to the support by pressing and heating. A known laminator or vacuum laminator can be used to accomplish the adhesion. In order to increase productivity, an autocut laminator can also be used. After the temporary support is peeled off, the photosensitive resin layer is exposed through a predetermined mask, the thermoplastic resin layer and the intermediate layer, and then removed. The photosensitive resin layer can be removed by, for example, dipping the same in a solvent or an aqueous developing solution (especially in an alkaline aqueous solution), spraying the photosensitive resin layer with a processing solution through a spray, rubbing the photosensitive resin layer with a brush, or by processing while applying ultrasonic waves.
A multicolor image can be formed by repeating this process several times using a photosensitive transfer recording material that includes several photosensitive resin layers of mutually different hues.
The photosensitive transfer recording material of the invention is mainly used in the production of color filters for liquid crystal displays, in the production of protecting layers in color filters, in the formation of multicolor images, and in the production of printed circuit boards.
When the photosensitive transfer recording material is used in the production of printed circuit boards, a known copper-clad laminate is used as the substrate. When the photosensitive transfer recording material is used in the production of color filters, a known glass plate or a soda glass plate having a silicon oxide film on the surface is used as the substrate.
When the invention is used in the production of printed circuit boards or color filters, air bubbles are not incorporated into the surroundings of prior pixels even if lamination is conducted at high speed, nor do deviations in lamination occur. Further, the film does not expand during coating. Accordingly, a printed circuit board or a color filter having fine surface conditions is obtained.